Broadband TEM-horn antenna

Abstract

This application relates to a compact broadband horn antenna. The antenna has a septum in the horn adjacent one side thereof. One embodiment consists of abutting, wedge-shaped, dielectric members having conducting coatings. A particular feed arrangement has a primary segment partitioned into quadrants with each quadrant having a conducting septum extending forwardly into a secondary section, to provide field uniformity. In an embodiment useful at frequencies above 1 GHz the septum curves upwardly at the horn mouth and is supported by an absorbing structure located just above the mouth of the horn. The other end of the septum is supported at the horn feed and the septum is otherwise unsupported along its length.

I claim: 
     
       1. A compact horn antenna comprising: two abutting dielectric members, wedge-shaped in side view with unequal wedge angles, the front faces of the dielectric members being curved and cooperating with one another to define a lens surface at the front of the horn;   the side and outer surfaces of the dielectric members being planar with conducting coatings;   a conductor sandwiched between abutting inner surfaces of the dielectric members and spaced from other conducting surfaces to form an insulated septum in the horn;   a first downwardly curved conducting member extending forwardly from the front edge of the lower conducting surface of the horn and a second upwardly curved conducting member extending forwardly from the front edge of the septum, the second conducting member being connected to the front edge of the upper conducting surface of the horn by terminating resistors.   
     
     
       2. An antenna as set out in claim 1 wherein the conductor sandwiched between the dielectric members is part of a circuit board containing active elements coupled to the conductor. 
     
     
       3. An antenna comprising a conducting, conical horn having a primary section adapted to be connected to a signal source and a secondary section; a pair of conducting partition walls dividing the primary section into four quadrants electrically isolated from one another;   each quadrant of the primary section having an insulated conducting septum formed by a sector of a cone arranged parallel to and spaced from the outer surface of the horn;   each conducting septum extending forwarding into the secondary section and each partition wall extending forwardly into the secondary section, the walls separating from one another and reducing in height;   whereby the partition walls cooperate with the septums to provide field uniformity at the output of the antenna.   
     
     
       4. The antenna of claim 3 further including a coupling between a coaxial line and one quadrant of the conical horn comprising: a conductive connection between the outer conductor of the coaxial line and the wall of the horn,   a conducting member of variable cross-section located inside and spaced from the walls of the horn with its smaller end connected to the center conductor of the feed line and its larger end connect to a septum, the cross-section of the conducting member being rectangular at its smaller end and varying smoothly to be of crescent shape mid-way along its length and arcuate at its larger end,   a pair of conducting plates extending forwardly from the larger end of the conducting member and diminishing to define a wedge configuration.   
     
     
       5. The antenna of claim 1, further comprising: an absorbing array positioned adjacent one edge of the horn mouth,   the free end of the septum curving upwardly at the mouth of the horn to terminate in the absorbing array.   
     
     
       6. The antenna of claim 5 wherein the edges of the septum adjacent the side walls of the horn are bent out of the plane of the septum to provide rigidity. 
     
     
       7. The antenna of claim 6 further including absorbing material located adjacent the bent edges of the septum. 
     
     
       8. The antenna of claim 5 wherein the edges of the septum adjacent the side walls of the horn are formed in V configuration, both arms of the V being bent out of the plane of the septum. 
     
     
       9. The antenna of claim 8 further including absorbing material located adjacent the bent edges of the septum. 
     
     
       10. A coupling between a coaxial line and one quadrant of a conical horn comprising: a conductive connection between the outer conductor of the coaxial line and the wall of the horn,   a conducting member of variable cross-section located inside and spaced from the walls of the horn with its smaller end connected to the center conductor of the feed line and its larger end connect to a septum, the cross-section of the conducting member being rectangular at its smaller end and varying smoothly to be of crescent shape mid-way along its length and arcuate at its larger end,   a pair of conducting plates extending forwardly from the larger end of the conducting member and diminishing to define a wedge configuration.   
     
     
       11. A horn antenna having a conducting septum within the horn electrically isolated from the walls of the horn and adjacent to and spaced from one wall of the horn, the edges of the septum adjacent the side walls of the horn being bent out of the plane of the septum to provide rigidity, an absorbing array positioned adjacent one edge of the horn mouth,   the forward end of the septum curving upwardly at the mouth of the horn to terminate in the absorbing array.   
     
     
       12. An antenna as set out in claim 11 further including absorbing material located adjacent the bent edges of the septum. 
     
     
       13. An antenna set out in claim 11 wherein the edges of the septum adjacent the side walls of the horn are formed in V configuration, both arms of the V being bent out of the plane of the septum. 
     
     
       14. An antenna as set out in claim 13 further including absorbing material located adjacent the bent edges of the septum.